U.S. patent number 10,391,505 [Application Number 15/540,502] was granted by the patent office on 2019-08-27 for spray nozzle apparatus for spray-drying applications.
This patent grant is currently assigned to Societe des Produits Nestle S.A.. The grantee listed for this patent is NESTEC S.A.. Invention is credited to Peter Erdmann, Peter Fankhauser, Martin Nydegger, Dale Richard Sanders, Christian Schmied, Michael Stranzinger, Gerhard Walthert.
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United States Patent |
10,391,505 |
Erdmann , et al. |
August 27, 2019 |
Spray nozzle apparatus for spray-drying applications
Abstract
The invention provides for an spray nozzle apparatus (1) for a
spray drying apparatus comprising a nozzle provided with at least
one nozzle orifice (26) for outputting spray droplets of a product
to be dried and a least one inlet orifice (24) for transferring
said product into a nozzle chamber (22), including an apparatus for
adjusting the size of outputted droplets inline during the spray
drying process.
Inventors: |
Erdmann; Peter (Bern,
CH), Fankhauser; Peter (Konolfingen, CH),
Nydegger; Martin (Konolfingen, CH), Sanders; Dale
Richard (Courgevaux, CH), Schmied; Christian
(N/A), Stranzinger; Michael (Munsingen, CH),
Walthert; Gerhard (Aeschlen, CH) |
Applicant: |
Name |
City |
State |
Country |
Type |
NESTEC S.A. |
Vevey |
N/A |
CH |
|
|
Assignee: |
Societe des Produits Nestle
S.A. (Vevey, CH)
|
Family
ID: |
52292727 |
Appl.
No.: |
15/540,502 |
Filed: |
December 23, 2015 |
PCT
Filed: |
December 23, 2015 |
PCT No.: |
PCT/EP2015/081224 |
371(c)(1),(2),(4) Date: |
June 28, 2017 |
PCT
Pub. No.: |
WO2016/107817 |
PCT
Pub. Date: |
July 07, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180036749 A1 |
Feb 8, 2018 |
|
Foreign Application Priority Data
|
|
|
|
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Dec 31, 2014 [EP] |
|
|
14200754 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F26B
3/12 (20130101); B05B 1/34 (20130101); B05B
1/3426 (20130101); B05B 1/3452 (20130101); B05B
1/3468 (20130101); B05B 1/3026 (20130101); F16K
31/047 (20130101); B05B 1/3402 (20180801); F16K
31/508 (20130101); A23C 1/04 (20130101) |
Current International
Class: |
B05B
1/30 (20060101); F26B 3/12 (20060101); B05B
1/34 (20060101); F16K 31/50 (20060101); A23C
1/04 (20060101); F16K 31/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
935495 |
|
Nov 1955 |
|
DE |
|
19617685 |
|
Nov 1997 |
|
DE |
|
9748496 |
|
Dec 1997 |
|
WO |
|
Other References
ESPACEnet translation of DE 935495 Obtained Dec. 6, 2018, (Year:
2018). cited by examiner.
|
Primary Examiner: Miller; Jonathan
Attorney, Agent or Firm: K&L Gates LLP
Claims
The invention claimed is:
1. A single phase spray nozzle apparatus for a spraying apparatus,
the nozzle apparatus comprising: a nozzle provided with at least
one nozzle orifice for outputting spray droplets of a product to be
dried and at least one inlet orifice for transferring the product
into a nozzle chamber, the nozzle chamber comprising walls defining
a volume of the nozzle chamber, the nozzle chamber further
comprising an apparatus for adjusting a size of the outputted spray
droplets inline during a spray drying process, the apparatus
comprises a plunger for adjusting the volume of the nozzle chamber
based on spray drying process parameters and product parameters
obtained inline during the spray drying process, the walls of the
nozzle chamber do not have a turbulence generating surface, and the
product to be dried has a viscosity between 1 and 1000 mPas; an
electric drive for adjusting geometry of the nozzle chamber, the
electric drive controlled by a control device based on the spray
drying process parameters and the product parameters obtained
inline; and a connecting sleeve releasably fixed to the electrical
drive and providing a longitudinal bore for rotatably accommodating
a hollow shaft which transfers a rotating motion of an output shaft
of the electrical drive to an adjusting pin driving the plunger
into and out of the nozzle chamber, wherein the nozzle chamber is
provided by a swirl chamber body inserted into an inner chamber of
a nozzle body, the nozzle body releasably fixed to the connecting
sleeve, the swirl chamber body is provided with an opening channel
arranged in correspondence to the at least one inlet orifice for
introducing the product into a swirl chamber of the swirl chamber
body, the swirl chamber is provided with a helicoidal spiral-type
tightening guiding face for accelerating the product into the
direction of the at least one nozzle orifice.
2. The nozzle apparatus according to claim 1, wherein the plunger
is movable into and out of the nozzle chamber by the electric
drive, thereby adjusting a volume and a height of the nozzle
chamber.
3. The nozzle apparatus according to claim 2, wherein the electric
drive comprises an electric motor rotatably driving the output
shaft, the rotation being transformed into a longitudinal motion of
the plunger via a threaded engagement between the output shaft and
the plunger.
4. The nozzle apparatus according to claim 1, wherein the plunger
is axially movable, and the adjusting pin is provided with a
longitudinally extending axial bore with an inner thread in
engagement with an outer thread of the plunger such that a rotating
motion of the adjusting pin is transformed into a longitudinal
motion of the plunger.
5. The nozzle apparatus according to claim 1, wherein the at least
one inlet orifice extends radially to the longitudinal axis of the
nozzle such that the product is transferred to the nozzle via a
tubing connected with the at least one inlet orifice.
6. The nozzle apparatus according to claim 1, wherein the at least
one nozzle orifice is equipped with a releasably mounted orifice
plate such that an opening diameter of the at least one nozzle
orifice is variable by replacing the orifice plate by a different
diameter orifice plate.
7. The nozzle apparatus according to claim 1, wherein a cone angle
of a spray mist produced by the outputted spray droplets and the
size of the outputted spray droplets are variable by axially moving
the plunger relative to the nozzle chamber.
8. A spray-drying apparatus comprising: a nozzle having at least
one nozzle orifice for outputting spray droplets of a product to be
dried and at least one inlet orifice for transferring the product
into a nozzle chamber, the nozzle chamber comprising walls defining
a volume of the nozzle chamber, the nozzle chamber further
comprising an apparatus for adjusting a size of the outputted spray
droplets inline during a spray drying process, the apparatus
comprises a plunger for adjusting the volume of the nozzle chamber
based on spray drying process parameters and product parameters
obtained inline during the spray drying process, the walls of the
nozzle chamber do not have a turbulence generating surface, and the
product to be dried has a viscosity between 1 and 1000 mPas; an
electric drive for adjusting geometry of the nozzle chamber, the
electric drive controlled by a control device based on the spray
drying process parameters and the product parameters obtained
inline; and a connecting sleeve releasably fixed to the electrical
drive and providing a longitudinal bore for rotatably accommodating
a hollow shaft which transfers a rotating motion of an output shaft
of the electrical drive to an adjusting pin driving the plunger
into and out of the nozzle chamber, wherein the nozzle chamber is
provided by a swirl chamber body inserted into an inner chamber of
a nozzle body, the nozzle body releasably fixed to the connecting
sleeve, the swirl chamber body is provided with an opening channel
arranged in correspondence to the at least one inlet orifice for
introducing the product into a swirl chamber of the swirl chamber
body, the swirl chamber is provided with a helicoidal spiral-type
tightening guiding face for accelerating the product into the
direction of the at least one nozzle orifice.
9. The spray-drying apparatus according to claim 8, wherein the
product is a paste, and the apparatus comprises an inline
differential pressure drop measuring apparatus for continuous
determination of a shear viscosity of the paste, the inline
differential pressure drop measuring apparatus provided in a bypass
to a processing line upstream of the nozzle.
10. The spray-drying apparatus according to claim 9, wherein the
bypass comprises a pump, a flow meter, and a differential pressure
tube.
11. A spray-drying process comprising: spraying a paste of a
product using a spray nozzle provided with at least one nozzle
orifice for outputting spray droplets of a product to be dried and
at least one inlet orifice for transferring the product into a
nozzle chamber, the nozzle chamber comprising walls defining a
volume of the nozzle chamber, the nozzle chamber further comprising
an apparatus for adjusting a size of the outputted spray droplets
inline during the spray drying process, the apparatus comprises a
plunger for adjusting the volume of the nozzle chamber based on
spray drying process parameters and product parameters obtained
inline during the spray drying process, the walls of the nozzle
chamber do not have a turbulence generating surface, and the
product to be dried has a viscosity between 1 and 1000 mPas, the
product is sprayed into a drying chamber; adjusting geometry of the
nozzle chamber using an electric drive controlled by a control
device based on the spray drying process parameters and the product
parameters obtained inline, wherein the adjusting of the geometry
of the nozzle chamber comprises transferring a rotating motion of
an output shaft of the electrical drive to an adjusting pin driving
the plunger into and out of the nozzle chamber, wherein a
connecting sleeve is releasably fixed to the electrical drive and
provides a longitudinal bore for rotatably accommodating a hollow
shaft which transfers the rotating motion, and the nozzle chamber
is provided by a swirl chamber body inserted into an inner chamber
of a nozzle body, the nozzle body releasably fixed to the
connecting sleeve, the swirl chamber body is provided with an
opening channel arranged in correspondence to the at least one
inlet orifice for introducing the product into a swirl chamber of
the swirl chamber body, the swirl chamber is provided with a
helicoidal spiral-type tightening guiding face for accelerating the
product into the direction of the at least one nozzle orifice and
providing hot gas to the drying chamber to dry the paste to a
powder.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a National Stage of International
Application No. PCT/EP2015/081224, filed on Dec. 23, 2015, which
claims priority to European Patent Application No. 14200754.1,
filed on Dec. 31, 2014, the entire contents of which are being
incorporated herein by reference.
The present invention is directed to a single phase spray nozzle
apparatus for spray-drying applications comprising a nozzle
provided with at least one nozzle orifice for outputting spray
droplets of a product to be dried and at least one inlet orifice
for transferring said product into a nozzle chamber and having an
apparatus for adjusting the size of outputted droplets inline
during the pray-drying process. The invention also relates to a
spray-drying apparatus comprising such a spray nozzle and a
spray-drying process in which such a spray nozzle is used.
The manufacturing of food powders is realized to a great extent by
means of spray drying. This process converts emulsions, suspensions
and dispersions into powder. Spray nozzles create droplets, which
are dried in hot air by evaporating water. The final powder
quality, the final powder texture, the dryer process design, the
drying efficiency, the walls fouling behaviour, the operational
safety, to name only a few characteristics, are directly linked to
the spray quality and thus the atomization process.
A variety of nozzles can be used. Single phase nozzles are
advantageous because, no addition of liquid or gas is required to
support the atomization of the product to be spray-dried. However,
atomization of high viscosity products is more difficult with such
single phase nozzles.
Known spray drying processes use atomization nozzles with fixed
geometries which cannot be adjusted inline to the process and
product conditions during start-up, manufacturing operation and
shut-down. Instead operators change the nozzle geometries prior to
the production cycle without the possibility to cover all the
manufacturing situations. Such nozzles are chosen according to
water tables. The manufacturing of food powders happens at
significantly higher viscosities compared to water. In addition, it
is desired to carry out the spray-drying process with the highest
possible total solid content in order to reduce the cost and energy
consumption of the process. Increasing the total solids in turn
increases the viscosity of the product to be spray-dried. Typical
spray viscosities of foods concentrate with high total solids are
within a range comprised between 1 to 1000 mPas. There is no known
single phase nozzle apparatus capable to compete with such a wide
range and in particular with the highest viscosities.
As an example, for dairy emulsions at concentrate total solids
above 50%, the concentrate viscosity increases in an exponential
slope with further increase of total solids. This fact causes
problems to spray-drying, if the concentrate viscosity exceeds a
design limit of the single phase atomizer nozzles. The design limit
is described by means of an atomizer air-core break-down, which
stops the creation of droplets and thus stops efficient
spray-drying and agglomeration of powders with a required texture.
Using prior art spray nozzle apparatus, air-core break downs within
atomizer nozzles cannot be determined visually, thus there is
currently no means to operate the spray-drying process at its best
point without facing issues, such as powder blockages in cones and
cyclones, wall fouling or atomizer beard formation, to name just a
few issues.
From WO 2007/071235 A1 there is known a nozzle arrangement and a
method of mounting the nozzle arrangement in the wall of a spray
drying apparatus.
This known nozzle arrangement comprises a longitudinally extending
nozzle lance through which material to be dried can be fed to the
nozzle orifice where it gets outputted in the form of droplets by a
stream of drying gas of a suitable kind.
At a longitudinal end of the known nozzle arrangement there are
arranged two discs which can be rotated in a manner relative to one
another. Both of the discs comprise a tapered inner cross section
such that a rotation of the discs relatively to each other makes
the distance between the discs becoming greater or smaller.
Since the upper one of these two discs is in abutment to a nozzle
tube which in turn carries the nozzle lance, the distance between
the end of the nozzle lance and the nozzle orifice can be varied.
Before starting the production process with this known nozzle
arrangement the two discs are rotated relative to each other to
adjust the above-mentioned distance.
Thus this known nozzle arrangement is similar to the nozzle
arrangement as described above in so far as the nozzle arrangement
has to be adjusted before the beginning of the manufacturing
process and can not be readjusted without an interruption of the
manufacturing process.
Since however the product and process conditions change from
start-up to shut-down of the process the quality of the product
achieved varies and product build-up can happen on the nozzle
itself and the walls of the drying chamber.
There is therefore a need for a spray nozzle apparatus which helps
to avoid these drawbacks.
According to a first aspect of the invention there is provided a
single phase spray nozzle apparatus for a spraying apparatus
comprising a nozzle provided with at least one nozzle orifice for
outputting spray droplets of a product to be dried and at least one
inlet orifice for transferring said product into a nozzle chamber,
characterized by an apparatus for adjusting the size of outputted
droplets inline during the spray drying process, characterized in
that the apparatus comprises a plunger for adjusting the volume of
said nozzle chamber based on spray drying process parameters and
product parameters obtained inline during the spray drying process,
further characterized in that the walls of the nozzle chamber do
not have a turbulence generating surface and in that the product to
be dried has a viscosity comprised between 1 and 1000 mPas,
preferably between 20 and 1000 mPas.
This means that the spray nozzle apparatus according to the
invention gives an inline means to control spray droplet sizes
during spray drying. The spray quality can be judged in terms of
the droplet size distribution and its corresponding droplet size
mean diameter, i.e. the Sauter diameter D.sub.32.
The spray nozzle according to the invention helps to achieve the
following main manufacturing objectives: a minimum Sauter diameter
for fastest and equilibrium water evaporation, an optimum powder
agglomeration for consistent powder quality, an equilibrium powder
particle size distribution for consistent powder quality, the
elimination of scorched particles for consistent powder quality,
minimal powder wall fouling, minimal spray nozzle fouling and
increased dryer safety because of the elimination of dripping and
elimination of scorched particles, as well as an operation window
for the atomizing nozzles, to spray within the design limits
without exceeding the so called air-core break-down.
According to an advantageous embodiment of the invention, the
apparatus comprises means for adjusting the nozzle chamber geometry
based on spray drying process parameters, like spray mass flow
rate, spray pressure and product parameters, like product density,
product shear viscosity, which parameters are obtained or evaluated
inline during the spray drying process.
Thus it is possible to adjust the nozzle geometry inline on the
basis of parameters responsible for the process yield and the
quality of the product achieved. Furthermore the downtimes of a
spray drying apparatus equipped with a spray nozzle apparatus
according to the invention can be reduced since cleaning times are
cut significantly thanks to minimised equipment fouling.
It is further advantageous that the walls of the nozzle chamber
have no turbulence-generating surfaces as such surfaces would
disturb the liquid film generation within the swirl chamber and
thus disturb the control of the droplet size.
The nozzle apparatus can be provided with an electrical drive
adjusting the chamber geometry, the drive being controlled by a
control device on the basis of spray drying process parameters and
product parameters as mentioned above. To modify the chamber
geometry, according to an advantageous embodiment of the invention,
the apparatus comprises a plunger for adjusting the volume of the
nozzle swirl-chamber.
By moving the plunger into and out of the nozzle chamber by the
electric drive an adjustment of the height of the nozzle
swirl-chamber is achieved. Thus by moving the plunger, the geometry
of the nozzle chamber can be modified inline during the
manufacturing process in relation to the product and process
parameters as mentioned above.
Movement of the plunger is achieved by the electric drive which in
turn is controlled by a control device like a programmable circuit.
This circuit transmits control signals to the electric drive as a
function of the above-mentioned parameters.
In order to achieve the above, according to an advantageous
embodiment of the invention the electric drive comprises an
electric motor rotatably driving an output shaft, the rotation
being transformed into a longitudinal motion of the plunger via a
threaded engagement between the output shaft and the plunger. Thus
a mechanical stable and easy to handle configuration is
achieved.
According to an embodiment of the invention, a connecting sleeve is
provided which is releasably fixed to the electric drive and is
equipped with a longitudinal bore for rotatably accommodating a
hollow shaft which transfers the rotating motion of an output shaft
of the electric drive to an adjusting pin driving the plunger
axially into and out of the nozzle chamber.
The adjusting pin is provided with a longitudinally extending bore
with an inner thread in engagement with an outer thread of the
plunger such that a rotating motion of the adjusting pin is
transformed in to a longitudinal motion of the axially movable
plunger.
According to an advantageous embodiment of the invention, the
nozzle chamber is provided by a swirl chamber body being inserted
into an inner chamber of a nozzle body, the nozzle body being
releasably fixed to the connecting sleeve mentioned above and the
swirl chamber body is provided with an opening channel which is
arranged in correspondence to the orifice for entering the material
into the swirl chamber of the swirl chamber body. This material can
for example be a paste for the production of dairy and nutrition
products.
The swirl chamber can be provided with a helicoidally tightening
guiding face for accelerating the paste into the direction of the
nozzle orifice to output the material droplets with high speed.
Since the material is incompressible, by the adjustable movement of
the plunger within the swirl chamber the cone angle of the spray
cone and the droplet diameter can be modified according to the
product and process parameters inline during the manufacturing
process of the product to be achieved.
According to an advantageous embodiment of the invention, the
orifice for inducing the material into the nozzle chamber extends
radially to the longitudinal axis of the nozzle and the product
material is being transferred to the nozzle via a tube being
connected to the orifice.
To enable a basic modification of the output characteristics of the
spray nozzle, the nozzle body is equipped with a releasably mounted
orifice plate such that the opening diameter of the nozzle orifice
is variable by replacing the orifice plate by a different diameter
orifice plate.
According to a preferred characteristic, a cone angle of a spray
mist produced by product droplets and the droplet size are variable
by axially moving the plunger relative to the nozzle chamber.
The spray nozzle of the invention allows controlling of the process
in an automated way, which enables to operate the atomization of
spray-dryers within the design limits. As a consequence a better
and more consistent process performance is achieved, with reduced
rework and more consistent powder quality properties. The spray
nozzle of the invention, which provides active atomization control
preferably triggered by an automation control software has been
identified to achieve best-point operation of spray-dryers.
According to a second aspect, the invention provides a spray-drying
apparatus comprising a spray nozzle of the invention as described
herein and further comprising an inline differential pressure drop
measuring apparatus for continuous determination of the shear
viscosity (.eta.) of a product paste having a viscosity in the
range of 1 to 1000 mPas, provided in a bypass to the processing
line upstream of the spray nozzle.
In an advantageous embodiment, the bypass comprises a pump, a flow
meter, a differential pressure tube and optionally a pulsation
damper. In another preferred embodiment, in the bypass, the shear
rate is greater than 1000 s.sup.-1 and the Reynolds number is
smaller than 2300.
The shear viscosity is used as input parameter to control the spray
nozzle. It allows inline control of the spray nozzle. Thus, it
allows inline control of the spray droplet size, via a stability
criterion composed of the spray mass flow rate Qm, the spray
pressure P the product density (.rho.) and the product viscosity
(.eta.).
Furthermore, the control of the spray nozzle thanks to in line
determination of the shear viscosity enables to achieve a
consistent powder agglomeration in the product during a production
cycle independent of the total amount of solid particles (TS) or
independent of mass flow rate fluctuations. By this method, a
process automation can be achieved through improved and simplified
reproducibility and reliability of product properties for different
spray-dryer types. A competitive production control is achieved via
advanced design of final powder properties like powder moisture,
tap density, final agglomerate size and agglomerate stability. Due
to the automation the production economy and process efficiency
(best-point operation) is also enhanced.
The inline differential pressure drop measuring apparatus enables
inline recording of product shear viscosities e.g. of coffee and
milk products before atomization with its specific product
characteristics such as highly viscous (for example above 1,
preferably above 20, more preferably above 100 mPas) and
shear-thinning flow behaviour (determination of 2.sup.nd Newtonian
plateau viscosity (n)). The inline shear viscosity information is
necessary to operate a controllable evaporator or spray-nozzle
inline in order to determine the best point configuration of the
evaporator or atomizer and warn in case of design limit achieved.
The inline differential pressure measurement apparatus allows a
calibration of the shear viscosity for Newtonian and in particular
Non-Newtonian shear-thinning fluids based on laboratory
rheometers.
Other techniques to measure the shear viscosity inline are either
underestimating or overestimating the predefined product shear
viscosities of dairy and nutrition products (via laboratory
rheometer). In particular for shear-thinning fluids, the
frequency-based measuring technique, the Coriolis forced measuring
method and the quartz-viscosimetry method do not give the
possibility to determine the 2nd Newtonian plateau viscosity of
shear-thinning fluids due to the lack of information concerning the
applied flow field of the method (and thus unknown shear
rates).
Thus, inline recording of the so called second Newtonian plateau
viscosity of Non-Newtonian food fluids is possible with the
differential pressure drop measuring apparatus and thus allows
calibration with predefined product shear viscosity rheograms,
which are found from laboratory rheometer measurements.
BRIEF DESCRIPTION OF THE FIGURES
In the following the invention will be described in further detail
by means of an embodiment thereof and the appended drawings.
FIG. 1 shows a partial sectional side view of an embodiment of a
spray nozzle apparatus according to the invention;
FIG. 2 shows a cross sectional view of a hollow shaft of the spray
nozzle apparatus of FIG. 1;
FIG. 3 shows a partial sectional view of an adjusting pin;
FIG. 4 shows a front view of the swirl chamber body of the spray
nozzle apparatus of FIG. 1; and
FIGS. 5 and 5A depict a side view and a front view (in the
direction of arrow A) of the plunger of the spray nozzle apparatus
of FIG. 1.
FIG. 6 is a flow chart of a process for controlling the spray
droplet size of a spray nozzle apparatus of the invention;
FIG. 7 is a flow chart of a differential pressure drop method that
can be carried out with the differential pressure drop measuring
apparatus as used in a preferred embodiment of the present
invention;
FIG. 8 shows a principle of a differential pressure drop measuring
apparatus as used in a preferred embodiment of the present
invention.
The spray nozzle apparatus 1 according to FIG. 1 comprises an
electric drive 2 provided with an interface (such as a Profibus
interface or Ethernet/IP interface) and a power supply (such as a
24V-DC power supply) at 3 and an electric motor 4 including a
transmission connected with 3.
The electric motor 4 drives an output shaft 5 in a rotating manner.
The output shaft 5 extends into a longitudinally extending inner
bore 6 of a hollow shaft 7 which is depicted in more detail in FIG.
2.
The hollow shaft 7 is rotatably accommodated in a longitudinally
extending inner bore 8 of a connecting sleeve 9 which can be fixed
to the housing of transmission 4 by bolts 10.
The inner bore 6 of the hollow shaft 7 is equipped with an inner
thread 11 which can be brought into a threaded engagement with an
outer thread 12 provided on an end piece of an adjusting pin
13--shown in more detail in FIG. 3--which can be inserted into the
inner bore 6 of the hollow shaft 7.
Opposite to the threaded terminal end 12 of the adjusting pin 13
there is provided a receiving section of the adjusting pin 13,
which is formed with an inner bore 14 equipped with an inner thread
15.
The inner thread 15 of the adjusting pin 13 serves to be brought
into a threaded engagement with an outer thread 16 of a plunger 17
more clearly shown in FIGS. 5 and 5A.
As can be seen from FIGS. 5 and 5A, the plunger 17 comprises an
outer circumferential surface section 18 with a helicoidally shaped
cross section corresponding to the shape and size of a receiving
section 19 of a swirl chamber body 20 accommodated in a nozzle body
23 which is mounted to the connecting sleeve 9 as shown in FIG.
4.
The swirl chamber body 20 comprises a lateral or tangential inlet
channel 21 for introducing paste material or the like into the
swirl chamber 22 of the swirl chamber body 20.
Material to be transported through the inlet channel 21 into the
swirl chamber 22 can enter the nozzle body 23 via a first orifice
24 or inlet orifice which extends radially to the common
longitudinal axis 28 of the nozzle body 23 and the connecting
sleeve 9. To this end there is a tube 25 connected to the first
orifice 24 of the nozzle body 23 defining an inlet opening of the
apparatus 1.
Paste or paste like material delivered to the nozzle body 23 via
the tube 25 enters the nozzle body 23 via the first orifice 24 and
enters the swirl chamber 22 via the inlet channel 21.
The swirl chamber 22 is equipped with an axially extending through
hole having an inner circumferential surface section with a
helicoidally shaped cross section, thus forming a helicoidal,
spiral type guiding face that serves to accelerate the material
into the direction of a second orifice 26 or nozzle orifice of the
nozzle body 23 defining an outlet opening of the apparatus 1. There
is an orifice plate 27 provided between the axial outlet of the
swirl chamber 22 and the second orifice 26 by which orifice plate
27 the opening angle of the spray cone can be adjusted.
FIG. 1 shows the plunger 17 closing the first orifice 24. Driving
the motor 3 makes the hollow shaft 7 rotate and thus also makes the
adjusting pin 13 rotate about its longitudinal axis. The plunger 17
is connected to the inner thread 15 of the adjusting pin 13 via the
outer thread 16 and can only execute a movement relative to the
swirl chamber body 20 along the longitudinal axis of the plunger 17
but can not rotate relative to the swirl chamber body 20. Thus a
rotation of the adjusting pin 13 is transformed into an axial
movement of the plunger 19 relative to the swirl chamber body
20.
By this movement of the plunger 18 the axial width of the first
orifice 24 and the geometry of the swirl chamber 22 and thus the
nozzle chamber can be modified. Since the electric drive 2 is
controlled by process and product parameters which in turn are
obtained or evaluated inline during the manufacturing process of
the powder to be achieved, the control takes place inline with the
manufacturing process of the powder. To achieve this, the control
circuit provides the electric drive 2 with signals such that the
plunger 17 is being moved axially in the direction of the
longitudinal axis 28 as shown in FIG. 1. By this movement of the
plunger 17 the spray droplet size of the material to be atomized
can be adjusted towards the minimum Sauter diameter possible for a
given set of input parameters.
Measuring these input parameters inline with the production process
of the powder enables it to adjust the droplet size towards the
minimum Sauter diameter possible inline and thus makes it possible
to consider the complete range of spray viscosities during the
production process of the powder to be produced.
In a particularly preferred embodiment of the present invention,
the input parameters which are measured inline with the production
process are as follows: flow rate of the product into the spraying
apparatus pipes towards the nozzle, pressure of the product into
the pipes towards the nozzle, viscosity of the product measured in
the pipes towards the nozzle, and/or finally density of the
product, that is also measured in the pipes of the apparatus
leading to the nozzle.
The product paste entering the swirl chamber through the inlet
channel 21 follows a helicoidal and spiral way due to the
spiral-type cross section design of the swirl chamber in a combined
circumferential and axial direction towards the nozzle orifice 26.
This design accelerates the traveling speed of the product paste
flow in the swirl chamber, provided that the mass flow of the
product paste is constant. The product paste is exiting the spray
nozzle through the orifice plate 27 and the nozzle orifice 26 as a
cone-shaped film 29 with a cone tip angle .alpha. wherein the film
29 atomizes into droplets forming a spray mist. The cone tip angle
.alpha. is directly proportional to the traveling speed of the
product paste in the nozzle orifice 26, i.e. the higher the
traveling speed is, the larger the cone tip angle becomes and the
smaller the droplets size.
A cone tip angle .alpha. of 0.degree. generates no atomization and,
in a realized example, a cone tip angle .alpha. of 100.degree.
generates droplets having a Sauter-diameter of D.sub.32=30 .mu.m.
The wider the cone tip angle .alpha. is, the smaller the droplets
become so that the droplet size can be controlled by the cone tip
angle .alpha. and thus by the traveling speed of the product paste
in the nozzle orifice 26. The invention should not be regarded as
being limited to the embodiment shown and described in the above
but various modifications and combinations of features may be
carried out without departing from the scope of the following
claims.
FIG. 6 is a flowchart of a process for controlling the spray
droplet size of an agglomeration spray nozzle apparatus of the
invention, when the processing line is provided with an inline
differential pressure drop measuring apparatus. The product paste
in FIG. 6 indicated as "concentrate" is delivered to a dosing point
30, which leads a part of the product paste stream into a bypass
line 32. The majority of the product paste stream is directed into
a main product paste line 34. The bypass line 32 is redirected into
the main product paste line 34 at a line junction 36 downstream of
a differential pressure drop measuring apparatus 38 provided in the
bypass line 32.
Downstream of the line junction 36 a mass flow meter 40, a density
meter 42 and a spray pressure probe 44 are provided in the main
product paste line. Downstream of the spray pressure probe 44 the
main product paste line 34 enters a spray nozzle apparatus 1
through tube 25. The product paste delivered to the spray nozzle
apparatus 1 is then sprayed into a spray drying chamber 46.
The differential pressure drop measuring apparatus 38 determines
the shear rate and the shear viscosity .eta. of the product paste
delivered to the spray nozzle, according to one preferred
embodiment of the invention. The data of the shear rate and shear
viscosity .eta. are delivered from the differential pressure drop
measuring apparatus 38 to a control device (SPS-control) 48. In the
same manner, the product paste mass flow rate Q.sub.m determined in
the mass flow meter 40, the product paste density .rho. determined
in the density meter 42 and the spray pressure P of the product
paste determined in the spray pressure probe 44 are also delivered
to the control device 48. The shear rate has to be greater than
1000 s.sup.-1.
Control device 48 comprises a computer which calculates an output
control parameter based on the above data delivered to the control
device 48 and on the basis of known spray nozzle geometry
parameters stored in a memory of the control device 48. The output
control parameter is delivered to the spray nozzle apparatus 1 in
order to adjust the swirl chamber piston 17 (plunger) to a
calculated position in order to obtain a desired swirl chamber
volume.
The following equations 1-7 describe the solving procedure how to
control the plunger position (given with h.sub.sc) based on a
change in the paste shear viscosity .eta..
Accordingly the solving procedure is applied for a change in mass
flow rate Qm and paste density .rho..
Universal Massflow-Characterisation of Pressure Swirl Nozzle
Flows:
.eta..times..times..times..times..times..times..times..rho..times..eta.
##EQU00001## The relation between spray pressure P and axial
position of the plunger (given with h.sub.sc) is derived for the
example of a shear viscosity change from .eta..sub.old to
.eta..sub.new:
.eta..eta..times..eta..eta..times. ##EQU00002## Solved for the
spray pressure ratio:
.eta..eta..times. ##EQU00003## In order to find a direct relation
between plunger position h.sub.sc and shear viscosity .eta., the
spray pressure ratio has to be found from another equation, see
equations 4-6 below: Universal Spray Droplet Size Characterisation
of Pressure Swirl Nozzle Sprays:
.times..times..times..function..times. ##EQU00004## Again, one can
derive the Spray Pressure Ratio with the consistency conditions
that D.sub.32-global-old and D.sub.32-global-new remain
constant:
.times..times..times..eta..eta..times..times..times. ##EQU00005##
And hence the solution, how to control the plunger height
h.sub.sc,new based on a current position h.sub.sc,old:
.eta..eta. ##EQU00006## Combining equations 3 and 6 one receives
the solution, how to control the spray pressure:
.eta..eta. ##EQU00007##
FIG. 7 is a flowchart of the differential pressure drop method that
can be applied with the inline differential pressure drop measuring
apparatus 38. A feed pump 50 is provided in the bypass line 32
downstream of dosing point 30. The feed pump 50 ensures a constant
feed-flow-rate in the differential pressure drop measuring
apparatus 38 to enable shear rates which cover the second Newtonian
viscosity plateau. Downstream of the feed pump 50 a mass flow meter
52 is provided through which the product paste in the bypass line
32 is directed into a pressure drop meter 54. The shear viscosity
(.eta.) of the product paste in the bypass line 32 is calculated
from the mass flow measured in the mass flow meter 52, the known
product density of the product paste and the pressure drop measured
in the pressure drop meter 54. This calculation is either made in a
computer (not shown) of the differential pressure drop measuring
apparatus 38 or, the respective data are delivered to the control
device 48 and the shear viscosity .eta. is calculated in the
computer of the control device 48. In order to consider the fact
that the pressure drop is measured in a bypass line 32 the bypass
mass flowrate is adjusted by the feed pump 50 until the shear-rate
is above 1000 s.sup.-1, so that the second Newtonian plateau
viscosity can be measured by the pressure drop-meter 54 within
laminar flow conditions.
A pulsation damper is also preferably provided in the bypass to
reduce the noise in the pressure determination.
In the present example the dosing point 30 regulates the bypass
flow rate to keep the bypass flow pressure <20 bar at laminar
flow conditions, with a Reynolds number below 2300.
FIG. 8 shows the principle of an inline differential pressure drop
measuring apparatus (pressure drop meter) that can advantageously
be provided upstream of the nozzle of the invention.
The pressure drop meter 100 comprises a tube having a fluid inlet
section 102 and a fluid outlet section 104 and three pressure drop
measuring sections 106, 108, 110 provided between the inlet section
102 and the outlet section 104. The first pressure drop measuring
section 106 which is close to the inlet section 102 has a first
internal diameter d.sub.1 and a first axial length l.sub.1. A first
differential pressure meter 112 measuring a first pressure drop
.DELTA.p.sub.1 is connected to the first pressure drop measuring
section 106 in a commonly known matter wherein the axial distance
L.sub.1 between the two static pressure measuring openings in the
wall of the first pressure drop measuring section 106 is
substantially equal to the length l.sub.1 of the first pressure
drop measuring section 106.
The second pressure drop measuring section 108 is provided
downstream of the first pressure drop measuring section 106. The
internal diameter d.sub.2 of the second pressure drop measuring
section 108 is smaller than the diameter d.sub.1 of the first
pressure drop measuring section. The length l.sub.2 of the second
pressure drop measuring section 108 is shorter than the length of
the first pressure drop measuring section 106. The second pressure
drop measuring section 108 comprises a second differential pressure
meter 114 measuring a second pressure drop .DELTA.p.sub.2 wherein
the distance L.sub.2 between the two static pressure measuring
openings in the wall of the second pressure drop measuring section
108 is shorter than the distance L.sub.1 of the first differential
pressure meter 112.
A third pressure drop measuring section 110 is provided downstream
of the second pressure drop measuring section 108 and the third
pressure drop measuring section 110 opens into the outlet section
104. The internal diameter d.sub.3 of the third pressure drop
measuring section 110 is smaller than the diameter d.sub.2 of the
second pressure drop measuring section 108 and the length l.sub.3
of the third pressure drop measuring section is shorter than the
length l.sub.2 of the second pressure drop measuring section. The
third pressure drop measuring section 110 comprises in a commonly
known manner a third differential pressure meter 116 measuring a
third pressure drop .DELTA.p.sub.3. The distance L.sub.3 between
the two static pressure measuring openings in the wall of the third
pressure drop measuring section 110 is shorter than the distance
L.sub.2 of the second differential pressure meter 114.
The differential pressure drop meter 100 allows the measurement of
three independent pressure drop recordings of the first, the second
and the third differential pressure drop meters. Utilizing these
three differential pressure drop probes in series, a single mass
flow rate causes three increasing wall shear rates with the
decreasing tube diameter.
The following equation 8 is used to calculate the shear viscosity
.eta. for laminar tube flows (Re<2300), applied to all 3
differential pressures .DELTA.p.sub.1, .DELTA.p.sub.2 and
.DELTA.p.sub.3 (respectively measured at 112, 114 and 116, FIG. 8),
by replacing .DELTA.p.sub.i and the corresponding tube dimensions
(R.sub.i and L.sub.i) in equation 8:
Only, if the shear viscosity .eta..sub.i is equal
(.eta..sub.1=.eta..sub.2=.eta..sub.3) between the 3 differential
pressures, the 2.sup.nd Newtonian shear viscosity is found and used
e.g. in equation 1 and 7, etc.
.eta..pi..DELTA..times..times..rho. ##EQU00008## with following
definitions of symbols: R.sub.i: tube radius (R.sub.1, R.sub.2 and
R.sub.3) in [m] .DELTA.p.sub.i: tube pressure drop (.DELTA.p.sub.1,
.DELTA.p.sub.2 and .DELTA.p.sub.3) in [Pa] .rho.: product density
in [kg/m3] Qm: mass flow rate in [kg/s] L.sub.i: tube length
(distance L.sub.1, L.sub.2 and L.sub.3) in [m]
TABLE-US-00001 TABLE 1 Abbreviations and formula Symbol,
Abbreviation Description Units D.sub.32,global Global Sauter
diameter as found [m] from PDA measurements of spray d.sub.sc Swirl
chamber diameter [m] (smallest diameter of swirl chamber spiral)
h.sub.sc Swirl chamber height [m] (axial height of swirl chamber)
d.sub.or Orifice diameter [m] (diameter of opening made in orifice
plate) b.sub.ch Width of swirl chamber inlet [m] channel (smallest
width of inlet channel which leads into the swirl chamber) We Weber
number .rho..times..times..sigma. ##EQU00009## -- Eu Euler number
.rho..times. ##EQU00010## -- Re Reynolds number
.rho..times..times..mu. ##EQU00011## -- u.sub.bulk Bulk velocity at
swirl chamber inlet .rho..times..times. ##EQU00012## [m/s] Qm Mass
flow rate [kg/s] P Spray pressure [Pa] .rho..sub.liquid Liquid
density [kg/m.sup.3] .eta..sub.liquid Liquid shear viscosity [Pa s]
.sigma..sub.liquid Surface tension [N/m] PDA Phase-Doppler
Anemometry --
* * * * *